Performance venues such as theaters, arenas, concert halls, auditoriums, schools, clubs, convention centers, and television studios can employ battens or trusses to suspend, elevate, and/or lower lighting, scenery, draperies, and other equipment that can be moved relative to a stage or floor.
Conventional lift systems may be configured such that a pulley, or loft block, mechanism is attached directly to an overhead building support. As a result, an undesired amount of horizontal stress can be placed on the overhead building supports to which the system and associated load are attached.
Ropes or cables utilized to raise and/or lower a batten or other load may be wound about and unwound from a drum connected to a lift system motor. In conventional lift systems, the cables may rub unevenly against adjacent cables as they are being wound about and unwound from the drum. Such uneven rubbing can cause friction that may increase the rate at which the cables, drum, and other components need to be serviced and/or replaced. In addition, such friction can cause increased noise that may be undesirable in certain performance environments.
Some conventional drums can have a size and/or coil cables about the drums such that a large space is needed in which to locate the drum in or about the lift system. In “yo-yo” type drums and “pile” type drums, cables coil about the drum vertically on top of themselves. For example, in a “pile” type drum, after the cable has wound completely across the face of the drum, it is forced up to a second layer at a flange on the side of the drum. The cable then winds back across the drum in the opposite direction. In order to advance across the drum, the cable must cross over two cable “notches” of the previous coil. Such “cross-over” subjects a cable to abrasion, crushing, and pinching as it is pushed over the two cable notches across the crown of the first cable layer. Such stress can cause erratic motion of the cables as they are wound up onto the drum and/or unwound from the drum. Such vertically stacked coils of cables in conventional drums contribute to the need for increased torque to wind and unwind cables on those drums.
Conventional lift systems can include a cable management system in which electrical wires in a cable are stacked in layers back and forth on top of each other. The wires can fold back and forth periodically on themselves in a “scissoring” or “switchback” fashion, for example, every few feet. One risk of folding wires back onto themselves repeatedly is that they can be undesirably pinched, and can become worn over time.
In some conventional cable management systems, the electrical wire cable is collected in a tray positioned on top of a batten as the batten is raised. Such a tray may be referred to as a “flip flop” tray, since a portion of the electrical wire cable can be “flipped” in one direction and then “flopped” back onto itself in the opposite direction. A disadvantage of allowing such wire cables to collect in a stacked fashion on top of a batten, particularly on one end of the batten, is that the collected cables can cause the batten to be top heavy, which may cause the batten to become unbalanced and undesirably alter the orientation of the batten and/or articles attached to the batten.
In some lift systems, cables coiled about a drum can lose tension, for example, from becoming disconnected from a batten and/or article being raised and/or lowered, or the batten or article striking an object in its path. As a result of slack tension on the cables, the cables may need to be retained in position about the drum during such an event.
Lift systems often include a braking mechanism 118 to stop movement of the cables and article attached to the cables, for example, in the event of loss of power to the lift system motor or other reason the article begins to fall out of control of the lift system. Some braking mechanism 118s can be less than totally reliable, requiring redundant braking systems, and can be noisy and tend to wear out quickly.